1. Field of Invention
The present invention relates to an improved coupling assembly of the type employed to connect a pipelaying stinger to a pipelaying vessel.
2. Description of Prior Art
In laying pipe offshore on the floor of a body of water from a floating vessel in the conventional manner, a pipelaying stinger is employed which extends outwardly from the vessel into the water to support the pipe as it descends towards the bottom. Normally the stinger is rotatably pinned to the pipelaying vessel at two spaced, connecting points, which are aligned to form a hinge. This allows pivotal movement of the stinger about a horizontal axis to the desired angular position for support of the pipe being laid.
Failure to provide a stinger to support the pipe may result in the weight of the pipe developing large stresses that can buckle or rupture the segment of the line suspended between the vessel and the ocean floor. The problem of proper pipe support is compounded significantly in deep water, in heavy seas or with large diameter pipe, requiring the use of substantially larger stingers. These elongated outwardly extending structures present severe problems in heavy seas or adverse weather conditions. Because of the size of the stinger, environmental forces acting on it create tremendous bending moments at the coupling, frequently leading to coupling failures. Accordingly, stingers are normally detachably connected to the vessel so that they can be separated from the vessel during heavy seas or other adverse weather conditions.
Disconnection and reconnection of the stinger from the vessel during heavy seas are, however, also complex tasks and pose the possibility of damage to either the vessel, stinger, or coupling therebetween. When one of the two spaced joints is connected or disconnected before the other, even a relatively small lateral movement of the stinger with respect to the vessel, due to the length of the stinger, will produce tremendous forces which often result in damage to the coupling. In heavy seas it is difficult to connect or disconnect the two joints simultaneously, and the likelihood of damage to the coupling, vessel or stinger is significant.